1. Field of The Invention
The present invention relates to a data display method in a graphic data processing system which has display data structured in the hierarchy of plural concept levels, especially to an improved method capable of displaying a drawing of the different concept levels selected in response to a window designated in a display screen.
2. Description of The Related Art
Generally a display screen, for example, in a computer aided design (CAD) system for the design of large scale integration circuits (LSI), has a limitation in the screen size available for display and therefore can not display a general drawing showing the whole structure of a LSI on a convenient scale for the design work.
Conventionally, to overcome this problem, there has been defined a window within the display screen. A drawing of a part of the LSI which is now being designed has been displayed in a main area of the display screen on a convenient scale, while, in the area of the window, a general drawing of the whole structure of the LSI has been displayed on a reduced scale in order to make sure of what part of the whole structure is now being worked on. A method and apparatus of this kind is disclosed in pp. 169 to 173 of the journal "PIXEL" No.14, 1983, for example.
By the way, the general drawing does not need to be referred to so often during the design work. Therefore, a window defined within the display screen is preferred to be variable in its size, whereby a part which is now being designed can be displayed on the convenient scale by reducing the size of the window, in case the present size of the window impedes the design work. In such a case, however, the rate of scale-down of the general drawing is often changed and becomes very large depending on circumstances. If the rate of scale-down becomes large to a certain extent, characters in a displayed drawing are defaced or pairs of lines therein become undistinguishable, so that the displayed drawing becomes very indistinct as a whole.
It is to be noted that, even in this case, the amount of data to be processed for the display does not change, and nevertheless the quality of the displayed graphic is degraded. The problem mentioned above results from the fact that the amount of data to be displayed does not change irrespective of decrease of the size of the designated window. Conversely, a certain amount of data is processed for the uninformative display. Accordingly the efficiency of the processing considerably decreases.